1. Field
The present invention relates generally to wireless charging, and more specifically to devices, systems, and methods related to portable wireless charging systems.
2. Background
Typically, each powered device such as a wireless electronic device requires its own wired charger and power source, which is usually an alternating current (AC) power outlet. Such a wired configuration becomes unwieldy when many devices need charging. Approaches are being developed that use over-the-air or wireless power transmission between a transmitter and a receiver coupled to the electronic device to be charged. The receive antenna collects the radiated power and rectifies it into usable power for powering the device or charging the battery of the device. Wireless energy transmission may be based on coupling between a transmit antenna, a receive antenna and a rectifying circuit embedded in the host electronic device to be powered or charged. Shortcomings arise when load resistance as seen by the wireless power receiver circuit in the host electronic device is small due to, for example, battery technologies or geometries that exhibit a low charging resistance. Such low charging resistances reduce the charging efficiency. Accordingly, there is a need to improve the charging efficiency for wireless power transfer to electronic devices that exhibit a low charging resistance.